J2ME and files

[bartosz666]

after I launch netbeans' mobile phone emulator and choose the middlet to execute in the emulator screen I got a question if I wish to execute a 'reading' operation on file. When I click 'Yes' the program instead of reading the file - immidiately ends working and comes back to midlet list... and the requested read of file and printing its conent doesn work...

below is the code:

Code:

/*
 * live.java
 *
 * Created on 12 styczeń 2008, 02:18
 */
 
package futbol24;
 
import java.io.IOException;
import javax.microedition.lcdui.*;
import javax.microedition.io.*; // do laczenia sie z serwerem
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
 
import com.sun.midp.io.j2me.storage.File;
import com.sun.perseus.platform.BufferedInputStream;
import java.io.*;
import javax.microedition.io.file.*;
 
/**
 *
 * @author  bart
 * @version
 */
public class live extends MIDlet implements CommandListener {
   
    public live() {
    }
   
    private Form helloForm;
    private TextBox helloTextBox;
    private StringItem helloStringItem;
    private Command exitCommand;
   
    private void initialize() throws IOException {
        getDisplay().setCurrent(get_helloForm());
 
    }
   
    public void commandAction(Command command, Displayable displayable) {                   
        if (displayable == helloForm) {                     
            if (command == exitCommand) {                   
                exitMIDlet();                       
            }                     
        }                   
    }
   
    public Display getDisplay() {                         
        return Display.getDisplay(this);
    }
   
    public void exitMIDlet() {                         
        getDisplay().setCurrent(null);
        destroyApp(true);
        notifyDestroyed();
    }
   
    static String getLine(InputStream is) {
        String linijka = "";
       
        try {
            byte b[] = new byte[1];
            int koniec;
            koniec = is.read(b);
           
            if( koniec != -1 ) {
                while((new String(b).equals("\r")==false) && koniec!=-1) //wczytuje cala linijke
                {
                    linijka+=new String(b);
                    koniec = is.read(b);
                }
            } else if(koniec==-1) {
                    return "EOF";
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
       
        return linijka;
    }
   
    public TextBox get_helloForm() throws IOException {
        if (helloForm == null) {
           
            HttpConnection sc = (HttpConnection)Connector.open("http://kolos.math.uni.lodz.pl/~bart/tekstowy.txt");
            InputStream is = sc.openInputStream();
           
            boolean flaga = true;
            String linijka;
            int a=0;
           
            while(flaga) {
                linijka = this.getLine(is);
                if(linijka.equals("EOF")) {
                    System.out.println("koniec pliku");
                    flaga = false;
                    break;
                } else {
                    helloTextBox.insert(linijka,helloTextBox.size());
                }
            }
           
        }
       
        return helloTextBox;
    }
   
    public Command get_exitCommand() {
        if (exitCommand == null) {                     
            exitCommand = new Command("Exit", Command.EXIT, 1);                     
        }                     
        return exitCommand;
    }
   
    public void startApp() {
 
            try {
                initialize();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
    }
   
    public void pauseApp() {
    }
   
    public void destroyApp(boolean unconditional) {
    }
   
}

[hobbyist]

I just had a quick read of your code and I do not see an instantiation of a TextBox object. So I guess the problem is that your TextBox object is null being returned from get_helloForm() method. In fact you are returning the global object helloTextBox which has not been instantiated. I think you should look to see if you are getting a nullPointerException.

[hobbyist]

Somewhere in your code you need:
helloTextBox = new TextBox(String title, String contents, int size, int type);

In your initialise() method you are:
getDisplay().setCurrent(get_helloForm());

I think that a null is being returned from get_helloForm() so a nullPointerException will be thrown when you try to setDisplay() in your initialize() method.